Nl (Unix)

nl
Operating system	Unix and Unix-like
Platform	Cross-platform
Type	Command
License	coreutils: GPLv3+

nl is a Unix utility for numbering lines, either from a file or from standard input, reproducing output on standard output.

History

nl is part of the X/Open Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX.1 and the Single Unix Specification. ^[1] It first appeared in System V release 2. ^[2]

The version of nl bundled in GNU coreutils was written by Scott Bartram and David MacKenzie. ^[3]

The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities. ^[4]

Syntax

The command has a number of switches:

• a - number all lines
• t - number lines with printable text only
• n - no line numbering
• string - number only those lines containing the regular expression defined in the string supplied.

The default applied switch is t.

nl also supports some command line options.

Example

$nltf 1echopresscr 2readcr 3done

The following example numbers only the lines that begin with a capital letter A (matching on the regular expression /^A/). filename is optional.

$ nl-bp^Afilename        apple    1  Apple       BANANA    2  Allspice       strawberry

It can be useful as an alternative to grep -n :

$ catsomefile aaaabbbbccccdddc$ nlsomefile|grepcccc     3 cccc

See also

• wc (Unix) – the word count command
• cat (Unix) – concatenate command (-n flag is equivalent to nl -a)
• List of Unix commands

References

1. nl  – Shell and Utilities Reference, The Single UNIX Specification , Version 5 from The Open Group
2. nl(1)  –  FreeBSD General Commands Manual
3. nl(1)  –  Linux General Commands Manual
4. "Native Win32 ports of some GNU utilities". unxutils.sourceforge.net.